A machine, such as a pneumatic compactor, includes a hydraulic propulsion system for providing motive power to one or more compaction members of the machine. The propulsion system may include hydraulic motors to drive the compaction members. The hydraulic motors and, thus, the compaction members and the machine may generally be operated with a specified speed range in order to limit overheating of the hydraulic motors. However, in some compaction applications, such as a chip sealing process, the machine may be required to be operated at a relatively higher speed in order to achieve desired process quality. Hence, there is a need for an improved method of cooling for such hydraulic propulsion systems.
U.S. Pat. No. 6,408,995 describes a hydraulic motor with a braking device. The braking device is acted upon by means of a control fluid via a brake release line. The brake release line is used to allow a continuous flushing flow of control fluid through the hydraulic motor at the same time as the release of the brake. The braking device is connected to the casing of the hydraulic motor. An outlet opening of the hydraulic motor leads via a leakage-oil line to the tank for the control fluid. In a hydraulic travel drive with a closed hydraulic circuit, the brake release line can be connected to the shut-off device for the servo adjustment system of the variable-displacement pump, and the leakage-oil line of the hydraulic motor can lead to the tank for the entire hydraulic fluid in the system. Since the control fluid coming from the tank for the hydraulic fluid is always cooler than the hydraulic fluid used to drive the hydraulic motor and circulating in the closed circuit, a cooling effect on the hydraulic motor is obtained.